Cancer is a public health concern. Despite advances in treatments such as chemotherapy, the prognosis for many cancers, including solid tumors, may be poor. It is estimated that about 559,650 Americans will die from cancer, corresponding to 1,500 deaths per day (Jemal et al., CA Cancer J. Clin., 57:43-66 (2007)). Accordingly, there exists an unmet need for additional treatments for cancer, particularly solid tumors.